1. The problem statement, all variables and given/known data Say something has an amount and it decreases by 20% a year. Lets say the starting amount is 100. Then, after 1 year youd expect the amount to be 80. The DE x'(t) = -.20x(t) would represent the above comment. I think. (x(t) is a function of the amount after time t.) However, if you solved that DE and found your function x(t) and plugged in 1 for t, you would not get 80. Why is this so?